81799973 has 2 divisors, whose sum is σ = 81799974. Its totient is φ = 81799972.

The previous prime is 81799897. The next prime is 81799987. The reversal of 81799973 is 37999718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78552769 + 3247204 = 8863^2 + 1802^2 .

It is a cyclic number.

It is not a de Polignac number, because 81799973 - 2¹⁰ = 81798949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81099973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40899986 + 40899987.

It is an arithmetic number, because the mean of its divisors is an integer number (40899987).

Almost surely, 2^81799973 is an apocalyptic number.

It is an amenable number.

81799973 is a deficient number, since it is larger than the sum of its proper divisors (1).

81799973 is an equidigital number, since it uses as much as digits as its factorization.

81799973 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 857304, while the sum is 53.

The square root of 81799973 is about 9044.3337510289. Note that the first 3 decimals coincide. The cubic root of 81799973 is about 434.0946033867.

The spelling of 81799973 in words is "eighty-one million, seven hundred ninety-nine thousand, nine hundred seventy-three".